The standard method for searching for new chemical compounds which can effectively modulate biological processes employs the screening of pre-existing compounds in assays which have been designed to test particular properties of the compound being screened. Similarly, in designing compounds having desired physiochemical properties for general chemical applications, numerous compounds must be individually prepared and tested.
To reduce the time and expense involved in preparing and screening a large number of compounds for biological activity or for desirable physiochemical properties, technology has been developed for providing libraries of compounds for the discovery of lead compounds. Current methods for generating large numbers of molecularly diverse compounds focus on the use of solid phase synthesis. The generation of combinatorial libraries of chemical compounds by employing solid phase synthesis is well known in the art. For example, Geysen, et al. (Proc. Natl. Acad. Sci. USA, 3998 (1984) describe the construction of multi-amino acid peptide libraries; Houghton, et al. (Nature, 354, 84 (1991) and PCT Patent Pub. No. WO 92/09300) describe the generation and use of synthetic peptide combinatorial libraries for basic research and drug discovery; Lam, et al. (Nature, 354, 82 (1991) and PCT Patent Pub. No. WO 92/0009 1) describe a method of synthesis of linear peptides on a solid support such as polystyrene or polyacrylamide resin.
The growing importance of combinatorial chemistry as an integral component of the drug discovery process has spurred extensive technological and synthetic advances in the field (Thompson, L. A.; Ellman, J. A. (1996) Chem. Rev. 96,555-600). Founded in peptide synthesis devised by Merrifield, solid phase chemistry has emerged as the preeminent method for construction of small molecule combinatorial libraries (see e.g. Merrifield, R. B. (1963) J. Am. Chem. Soc. 85, 2149-2154; (a) Terrett, N. K.; Gardner, M.; Gordon, D. W.; Kobylecki, R. J.; Steele, J. (1995) Tetrahedron 51(30), 8135-8173. (b) Gordon, E. M.; Barrett, R. W.; Dower, W. J.; Fodor, S. P. A.; Gallop, M. A. (1994) J. Med Chem. 37,1385-1401.).
Unfortunately, the generation of chemical compounds for combinatorial chemical libraries is a labor intensive process. Working with numerous reaction vessels concurrently is very difficult and time consuming. In the past, multiple solid phase reactions were conducted by heating a substrate attached to resin beads with appropriate reagents and solvents in a test tube immersed in a hot oil bath with a rotating magnetic stir bar. Draining was accomplished by pouring the contents of the test tube through a filter. Back and forth operation between reacting and draining operations was very tedious and potentially exposed the reaction mixture to air. Certain chemical processes also required that the chemical reagents be kept under an inert or anhydrous atmosphere to prevent reactive groups from reacting with molecular oxygen, water vapor, or other agents commonly found in air. Accordingly, there is a need for a device which would provide heating and/or cooling, mixing, a closed environment for moisture sensitive and air sensitive chemistries, easy draining, rapid liquid metering, and rinsing of a plurality of reaction vessels.
While certain chemical synthesizers are known in the art, these synthesizers fail to provide the desired features necessary to efficiently generate large numbers of chemical compounds.
The present invention is directed to an apparatus which is useful for the synthesis of chemical compounds, for example, for the preparation of multiple discrete compounds for combinatorial libraries of compounds. The present invention is useful for developing new drugs and chemical entities. The invention is useful for rapidly generating and systematically synthesizing large numbers of molecules that may vary in their chemical structure or composition. The invention is further useful for randomly generating a large number of candidate compounds, then later optimizing those compounds which exhibit the most desirable properties.
The present invention provides a interface head which allows a user to add reagents and wash solvents to a reaction vessel. Typically, the interface head can engage a plurality of these reaction vessels mounted in a cassette or frame and is adapted to removably engage passages leading into the reaction vessel. The interface head allows a user to manually inject materials into the plurality of passageways in the head which are fluidly coupled to the reaction vessel. The interface head has a septa valve which opens and closes inlets of the plurality of passageways. The septa valve comprises an elongate member with a septum portion and a plurality of septum ports. The elongate member is slidable between a first position wherein at least one inlet of the passageways in the interface head is sealed by the septum portion and a second position wherein said at least one inlet is aligned with one of the ports to allow delivery of materials from the inlet into the reaction vessel. The septum portion is penetrable by needles and thus allows access for needle/syringe type delivery devices.
Advantageously, the interface head may be manually operated to provide ease of use for operators. The interface head, of course, may also be adapted to be used with automated systems, such as mounted on a robotic manipulator. The interface, however, may also be used to add reagents to reaction vessels in situations where reagents in an automated procedure were left out or additional solvent washes are needed. The interface head may also be adapted to extract finished material from within reaction vessels. Guide pins may be provided to assist in the alignment of the interface head with a cassette or housing used to contain the reaction vessels. In some embodiments, the device is essentially a manifold having a septa valve providing access to a pipet or reagent injector, a coupling tube to interface with a passage leading to the reaction vessel, and a connector for actuating the valve of the reaction vessel.
In preferred embodiments, the interface head of the present invention allows for simultaneous introduction of wash fluids into a plurality reaction vessels. Typically, the reaction vessels each having a first upper port and a second upper port. The interface head is adapted to removably engage a plurality of passages each leading to the first upper port on each of the reaction vessels. A plurality of infusion passages in the interface head each have outlets adapted to be positioned to feed into the reaction vessels. Fluid introduced into a common infusion passage defined within the interface head may be simultaneously delivered into the infusion passages and into the reaction vessels. The interface head preferably has an interface tube adapted to form a radial seal with the passage leading to a first upper port of the reaction vessel, where the infusion passage is downstream of the common passage. Flow from the common passage into the infusion passages is preferably controlled by a membrane valve covering the common passage. The common passage is typically a groove on a surface of a manifold in the interface head. The interface head may also include a plurality of vent passages and a common vent passage defined by the interface head to remove materials from the plurality of reaction vessels.
In another aspect of the present invention, a method is provided for providing a substantially equal distribution of fluids to a plurality of reaction vessels during one fill cycle. The method includes flowing fluid along a common passage to the plurality of reaction vessels, where the common passage has a plurality of individual passageways opening into the reaction vessels. The reaction vessels are filled by using back pressure in the reaction vessels to direct flow to the reaction vessels with the least amount of fluid and back pressure. Back pressure in the reaction vessels are relieved by opening reaction vessel vent valves to allow the reaction vessels to continue filling with fluid. Without doing so, the back pressure may substantially slow delivery of fluids into the reaction vessels.
The structure and function of the preferred embodiments can best be understood by reference to the drawings. The reader will note that the same reference numerals appear in multiple figures. Where this is the case, the numerals refer to the same or corresponding structure in those figures.